I'm not a real firm believer in the cycle in a bottle.
If you want to spend the money on it, it's a risk. But fish flakes are the only proven method.
I also disagree wholeheartedly that you would reinforce three fish in there which need a 20 gallon tank.
It is a best case temporary senario. But it isn't how you should keep them. Each fish needs to be returned.
MABJ's iDevice used for this message :p